The present invention relates generally to an antistatic agent for thermoplastic polymers and to thermoplastic compositions containing such an agent.
Many thermoplastic compositions, including ABS compositions, exhibit relatively slow electrostatic charge dissipation rates which make them unacceptable for many applications, i.e., housing for optical and magnetic recording media, medical devices and military equipment.
One method used to raise the electrostatic charge dissipation rates of these compositions is to incorporate a hydrophilic, moderately incompatible material with antistatic properties into the composition.
Types of these so-called "internal" antistatic materials or agents include ethoxylated amine chemicals and homopolymers and copolymers of ethylene oxide, such as polyethylene oxide and epichlorohydrin rubber.
These antistatic agents function by continually migrating to the surface of the composition, because of their limited compatibility, to form a continuous film on the surface. Moisture is attracted to the surface of the composition by these antistatic agents thereby decreasing the static charge.
Unfortunately, the antistatic agents currently known have certain disadvantages. Included among these disadvantages are degradation of the compositions physical and mechanical properties due to the presence of the antistatic agent; inadequate electrostatic charge dissipation rates; functional dependence on the amount of moisture in the surrounding atmosphere; and reduction over time of the antistatic agents ability to decay surface charge as a result of wiping, rinsing, aging or blooming of the agent.
It is therefore a primary object of the present invention to provide an antistatic agent that is durable; serves to maintain or enhance the host compositions' mechanical properties; and which produces a highly conductive antistatic thermoplastic composition irrespective of the amount of moisture in the surrounding atmosphere.
It is a further object of the present invention to provide an antistatic thermoplastic composition that incorporates the inventive antistatic agent.